Today's integrated circuits include a vast number of devices. Smaller devices are key to enhance performance and to improve reliability. As MOSFET (Metal Oxide Semiconductor Field-Effect-Transistor, a name with historic connotations meaning in general an insulated gate Field-Effect-Transistor) devices are being scaled down, the technology becomes more complex. There is great difficulty in maintaining performance improvements for devices of deeply submicron generations. Many avenues are being explored for keeping device performance improvements on track. Along the path of seeking ever higher device performance, downscaling of the MOSFET devices is the established guiding principle.
Downscaling dimensions naturally leads to shallower and lower doped device (source and drain) junctions, thereby increasing the parasitic resistance of the device. This happens at a time when performance dictates exactly the opposite, namely the reduction of parasitic resistance of junctions, especially that of the source junction. Spreading resistance, junction extension edge resistance, contact resistance at silicon and metal silicide interfaces, are all components of the parasitic resistance of junctions. To reduce these resistances, abrupt dopant profiles and high electrical activation are required, all the while maintaining the shallow junction profiles.
Usual techniques of the art for obtaining shallow junctions involve the implantation of the necessary dopants, such as boron (B), arsenic (As), phosphorous (P), and others, in a high dosage and at ultra-low energies, followed by a spike-Rapid Thermal Annealing (spike-RTA ) to activate these dopants. However, the high thermal energy of spike-RTA annealing results in high defect generation in junctions, resulting in fast dopants diffusion through defects. As a consequence, the junctions are no longer shallow and also become electrically leaky.